Myrmeciza exsul

Isler, Morton L., Bravo, Gustavo A. & Brumfield, Robb T., 2013, Taxonomic revision of Myrmeciza (Aves: Passeriformes: Thamnophilidae) into 12 genera based on phylogenetic, morphological, behavioral, and ecological data, Zootaxa 3717 (4), pp. 469-497 : 487-488

exsul clade

Phylogenetic relationships.— This clade of species currently placed in Myrmeciza includes M. exsul (Sclater) as sister to the rest, and M. griseiceps (Chapman) as sister of a well-supported, although internally unresolved, clade consisting of M. berlepschi (Hartert) , M. nigricauda (Salvin and Godman) ; M. palliata (Todd) and M. laemosticta Salvin ( Figs. 1 and 2 ; Chaves et al. 2010). Until recently, nigricauda , palliata , and laemosticta were considered conspecific, and, given their morphological similarity, their plumage and morphometric data are combined as the laemosticta group.

Biogeography. —The exsul clade is trans-Andean. Species occur from Nicaragua to the western slopes of the Andes in extreme northwest Peru; exsul and berlepschi inhabit lowlands and the remaining species mostly foothills although griseiceps ranges to 3000 m. Myrmeciza exsul and berlepschi are sympatric in Colombia; exsul and nigricauda overlap elevationally; berlepschi and nigricauda appear to be elevationally parapatric. All other species are allopatric.

Plumage.—Except for the black berlepschi , the clade is gray anteriorly and brown (typically dark reddishbrown) posteriorly with wing coverts tipped white in at least one sex (except some subspecies of exsul ) and white interscapular patches (small in exsul ). Females in the laemosticta group are distinguished by black throats spotted white. Male griseiceps has a large black breast patch and graduated tail tipped white; the female has a white throat and breast streaked pale gray. Bare blue periorbital skin distinguishes exsul . Male berlepschi lacks white wing covert spots that are present in the female, which also has white spots from throat to upper belly.

Morphometrics.—Although the tail of berlepschi is slightly shorter and its bill slightly longer, species in the clade are similar in their measurements except for griseiceps ( Table 2 ). Myrmeciza griseiceps is smaller except its tail is longer which creates a high ratio between tail length and wing and total length. In addition, its bill is thinner which produces a low bill depth/bill length ratio ( Table 3).

Loudsongs.—The structure of male loudsongs of laemosticta , berlepschi , nigricauda , and palliata are similar: a countable series of abrupt notes shaped like a sharply peaked chevron. Female loudsongs of all four species can readily be distinguished from those of males, especially by their longer and flatter notes. Loudsongs of griseiceps (a rapid trill) and exsul (two-noted) differ from those of berlepschi and the laemosticta group as well as from one another, and their female songs are more similar to those of their respective males.

Habitat.—All species inhabit dense, tangled vegetation, the type of vegetation varying with conditions within their ranges: exsul in dense, tangled vegetation in humid lowland forest and mature second growth, sometimes in areas with more open undergrowth; griseiceps in patches of dense montane forest especially bamboo patches; berlepschi in heavily vegetated lowland forest, especially at borders and light gaps, and dense second growth; the laemosticta group in wet forest in foothills, often in ravines and steep slopes with tangled treefalls and landslides.

Foraging behavior.—All species except griseiceps forage primarily on the ground, hopping up to low substrates mostly <1 m (although nigricauda and berlepschi are poorly known). In contrast, griseiceps forages mostly 2-7 m up.

Tail and wing movements.—All species pound their tails down and raise them back slowly.

Nest architecture.— Myrmeciza exsul builds a bulky bottom-supported cup placed on a foundation of plants and debris <0.4 m off the ground. The nest of laemosticta is a rim-supported cup built with flexible fibers and placed on shrubs 30–50 cm off the ground (Greeney et al. 2013). One minimally described nest, likely to be palliata given the record’s locality, was said to be a cup placed low in a shrub.

Discussion.—The issue is whether to consolidate these six species in a single genus or to place exsul , griseiceps , and the laemosticta group and berlepschi in three genera. The question is complicated by griseiceps whose unique morphology led Hellmayr to conclude that the species “is extremely puzzling in its affinities.” (Cory and Hellmayr 1924). The phylogeny embeds griseiceps between exsul and the clade consisting of berlepschi , nigricauda , palliata and laemosticta . These four species evidence similar morphology and behavior. Myrmeciza exsul is close to this group in morphology and behavior, as was suggested earlier by Robbins and Ridgely (1991). However, nest architecture supports distinguishing exsul from the laemosticta clade.

Taxonomic Recommendations.—Differences in plumage, morphometrics, foraging behavior, and loudsong structure between griseiceps and other members of the exsul clade require that griseiceps be placed in a monotypic genus. Despite the similarities between exsul and berlepschi and the laemosticta group, exsul then must be placed in a monotypic genus to avoid paraphyletic genera; differences in plumage, vocalizations, and nest architecture also support such treatment. We recommend that berlepschi and the laemosticta group be considered congeneric. The appropriate name for this genus is Sipia . New generic names are needed for exsul and griseiceps .

Figures

FIGURE 1. Maximum-likelihood tree of a subset of the Thamnophilinae, showing that Myrmeciza is polyphyletic (species names in these clades are emboldened). Members of Myrmeciza are placed in eight different well-supported clades in the Microrhopiini, Pithyini, and Pyriglenini. The color of the circles at nodes indicates bootstrap support values,> 70 % (black), 50 - 70 % (gray), <50 % (white).

FIGURE 2. Bayesian consensus tree of a subset of the Thamnophilinae, showing that Myrmeciza is polyphyletic (species names in these clades are emboldened). Members of Myrmeciza are placed in eight different well-supported clades in the Microrhopiini, Pithyini, and Pyriglenini. The color of the circles at nodes indicates posterior probability support,> 0.95 (black), 0.95 – 0.75 (gray), <0.75 (white).